Emulsions are generally stabilise by: 1. Repulsive charges on the surface of the dispersed phase that is surrounded bv a continuous phase.

2. In addition, there is an adsorbed film that is mainly wetted by the continuous phase and acts as a physical barrier to prevent contact between the dispersed droplets.

Ref : J. E. Strassner. Effect of pH on Interfacial Films and Stability of Crude Oil-Water Emulsions. SPE. 303-312 (1967) The adsorbed film is made up of natural surfactants, chemical additives, solids, other high-molecular compounds/polymers, as well as adsorbed ions. This will give the small, dispersed droplets in the continuous medium the same electrical charge, and they will thus repel each other, preventing coalescence of these particles.

Several attempts have been made to break more or less stable emulsions. Attempts that are previously known have often been successful in terms of breaking up emulsions that must be regarded as belonging in the area less stable to stable, but have often exhibited limitations in the face of highly stable emulsions of the type described above.

Mechanically generated emulsions of refined oils without natural surfactants/chemical additives and water may become stable if the particle sizes becomes sufficiently small (< 10 pm). Under these conditions, electrical charges in the dispersed phase will become the dominant stabilising factor.

Stable emulsions in the form of oil based slopmud emulsions from drilling activities consist mainly of used drilling mud mixed in with jet water and other waste/wastewater from the offshore oil activity. Slopmud typically contains 10-20 vol. ° Ó oil, 55-75 vol. % water and 5-12 vol. % solids. Oily drilling mud may in addition contain a certain amount of special chemicals in order to impart to the mud those qualities that are required in order to allow the mud to be used for drilling. The solids chiefly consists of clay (modified bentonite) that has been made hydrophobic by means of quaternary ammonium compounds with a special chemical composition.

In addition, there is also baryte. which is used as a weighting agent and to which chemicals have also been added in order to make it hydrophobic and stable during drilling. It also contains small amounts of drilling fines, which will be crushed cuttings.

The content of surface-active chemicals in the drilling mud affects the wetting characteristics of the solids, in addition to having a stabilising effect on the emulsion under the existing alkaline pH-conditions.

Today, oily slopmud emulsions are treated firstly through pH conditioning, which partly alters the wetting characteristics of the solids and thereby destabilises the emulsion.

Oily drilling mud is normally conditioned by lowering the pH value. Following conditioning, the emulsion is allowed to settle in a tank. This results in an oil layer at the top of the vessel, followed by a water phase in the middle, which may be extracted and treated before the water is discharged. The remaining emulsion at the bottom of the tank may now have a solids content of up to twice the initial content. A solids content of 12-15 vol. % is not unusual by such a method, when the initial solids content is 6-8 vol.

%.

The remaining mud phase may now be mixed with oily cuttings with a high solids content and treated thermally in a fluidised bed unit in which the water evaporates and the oil/chemicals evaporates/is cracked, so that the base oil can be recovered and the resulting solids contain only a small residual amount of hydrocarbons (< 500 ppm).

Refinery sludge often consist of stable solids-stabilized emulsions, and are currently treated by means of a centrifuge in order to remove as much water as possible, following conditioning with various types of chemical additives. Refinery sludge containing crude oil contains natural surfactants in the form of resins and asphaltenes that, in combination with wax, additives and solids may contribute to the formation of highly stable emulsions. The solids in the various types of refinery sludge normally amount to about 1-10 vol. %, and may be a mixture of coke particles, rust and salt, as well as mud and silt. The recovered oil is normally as a resource at the refinery. The remaining sludge, the volume of which is reduced by up to 30-50 %, is incinerated under conditions of added energy, e. g. in an incinerator, so as to leave an ash residue that must be disposed of, often at considerable costs.

Norwegian patent application no. 19984054 describes a method and equipment for destabilising mechanical emulsions through mechanical removal of electrical charges.

This is a method that has proven to be suitable for breaking up a number of types of emulsions that are not stabilised by natural surfactants in the form of resin/asphaltene compounds, chemical additives and solids.

In US 5 100 559, a method is described by which emulsions are cracked by heating the mixture to a temperature of 200 ° C at a high pressure. The mixture is kept at this high temperature and high pressure until the phases have separated. The method normally requires a large amount of energy and is therefore not recommended in cases of highly stable and difficult emulsions. No mention is made of separation of solids.

EP 141 529 describes the breaking up of emulsions by means of heat. Heat is added to the tank by means of inclined heating rods that extend into the emulsion. After the emulsion has been broken by this heat treatment, the components are separated by means of their different densities. Vapour from oil fractions with a low boiling point is extracted at the top of the vessel. Treated water and oil is removed from the vessel at the bottom and the top of the vessel respectively. No mention is made of separation of solids.

NO 159 575 describes a method of reducing the content of water in oil mud. The oil mud in a vessel is kept at a negative pressure and a temperature that is higher than the boiling point of water at this pressure. Stirring of the mud takes place through mud being drained from the bottom of the vessel and fed into the vessel above the surface of the liquid, where the incoming mud is sprayed against an impact plate before running down. Water vapour is drawn off at the top of the vessel and liquefied through cooling.

The aim of this invention is to reduce the water content to such an extent that the mud may be used as fuel. No mention is made of separation of solids or the possibility of separating oil and water in the vessel.

NO 161 076 describes an apparatus for collection and disintegration of viscous petroleum emulsions, in which a demulsifying agent is used to break up the emulsion.

The novelty of this invention is reported to be a combination of a mixing device in which the demulsifying agent is mixed into the emulsion before the emulsion reaches the collecting vessel, and a negative pressure in the collecting vessel for sucking up the emulsion.

GB 1 409 045 describes a method and an apparatus for coalescence of dispersed droplets. The emulsion is passed through a special packing or across a baffle where the emulsion is brought into contact with two different materials, one with a high surface energy and one with a low surface energy.

WO 95/10345 also describes a treatment vessel in which an emulsion is broken up by means of heat, and in which oil and water is allowed to settle before being extracted as "pure"phases.

SU 1755861 A1 also describes a vessel for breaking oil/water emulsions. The incoming emulsion is introduced above the surface of the water in the vessel. The incoming emulsion is passed across an undulating dish over which is mounted bell shaped bodies with spark plugs. The emulsion drains from the dish into the liquid below, where oil and water is allowed to settle prior to the"pure"phases being extracted.

SU 1214-135 A describes a solution in which the emulsion is sprayed into a vessel against a screen above the surface of the liquid, in the form of a jet. The impact against the screen deforms the droplets of the emulsion and breaks the emulsion. The liquid runs down the screen that extends below the liquid surface, where oil and water is separated by sedimentation. Vapour is extracted at the top of the vessel. No mention is made of temperature and pressure. Also, no mention is made of separation of solids.

US 4 938 876 describes a method of separating solids-stabilised oil/water emulsions, in which method the emulsion is heated at a high pressure (7 bar) and high temperature (170 ° C) and then subjected to a rapid pressure drop (to approximately 1 bar) by passing the mass through a nozzle into a large volume vessel. During this operation, water and light oil components evaporate off, and the temperature in the vessel falls to approximately 109-115 ° C. Solids are separated out by means of hydrocyclones and filters, while oil and water are separated by a continuous centrifuge. Preferably, use is made of flocculants in order to ensure efficient separation of solids.

The known techniques that are represented by the above publications are inadequate when it comes to separating highly stable emulsions in the form of certain types of refinery sludge, mud/slop emulsions, and other types of problem mud such as oil mud from steel mills and so-called"opportunity"wastes, which are organic wastes that are difficult to handle and that accumulate at special disposal sites in the absence of other alternatives.

Therefore it is an object of the present invention to provide a method of splitting highly stable emulsions comprising oil, water and solids.

For emulsions containing considerable amounts of solids, it is an object to separate out the solids in a fraction with the highest possible solids content, which gives the smallest possible volume for further treatment. The solids may after further treatment be reused or alternatively disposed of.

Moreover, it is desirable to be able to separate the water phase and the oil phase, such that these become sufficiently clean to allow the oil to be reused and the water to be discharged into nature with a minimum of aftertreatment.

It is therefore an object of the present invention to provide a method of separating the components oil, water and solids from stable emulsions in such a manner that the resulting oil and water phases are more or less free of particles, while at the same time producing a solids phase with a considerable solids content (up to 60 vol. %) without the use of other technologies in the form of centrifuges and hydrocyclones. It is also desirable that no organic additives be required, and that the method is not sensitive to foreign matter in the form of fibrous materials.

According to the invention, this object is achieved by a method of separating oil, water and solids from oily feeds in the form of emulsions and muds, where the feed has first been conditioned through pH regulation in a known manner in order to destabilise it, where the feed is first heated by being passed through an externally heated pipe; the heated feed is then led into a vacuum tank partially filled with treated feed that is undergoing final treatment in the form of settling, so that a particle-rich fraction is deposited at the bottom of the tank underneath a liquid phase with a reduced solids content, where there is a vapour pocket at the top end of the tank, and where the pressure in the vacuum tank is lower than atmospheric pressure; vapourised liquid is extracted from the vapour pocket, liquefied and treated further; the solids are allowed to settle before being removed from the bottom of the vacuum tank for further treatment; liquid is extracted from the liquid phase for further treatment.

Heating the feed by passing it through a pipe that is heated from the outside means that all the components of the feed are brought into contact with the surface of the pipe, ensuring that all the components of the feed are heated to approximately the same temperature. In addition, static charges that may be present in some of the feed components will be discharged upon contact with the pipe surface.

The pipe through which the feed is passed is preferably from about more than 25 m long, more preferably more than 50 m long, and most preferably more than 100 m long.

The feed is preferably heated to a temperature of from 60 to 120 °C, preferably from 80 to 110°C.

It is preferred that the absolute pressure in the vacuum tank be from 0.9 to 0.1 bar, more preferably from 0.8 to 0.3 bar, and most preferably about 0.5 bar.

According to a first preferred embodiment of the present invention, the feed is introduced at or near the top of the vacuum tank and sprayed out against the walls of the vacuum tank, above the liquid surface.

According to a second preferred embodiment, the feed is introduced into the vacuum tank immediately below the liquid surface. For this embodiment, it is preferable that the feed be led into a region that is horizontally delimited against the remaining contents of the tank.

The feed is preferably subjected to vacuum conditions in the heater.

It is a further object to provide a device for implementation of the method.

According to the invention, this is achieved by a device for separating oil, water and solids from an emulsion, that comprises a heater comprising an externally heated pipe for heating of the emulsion; a vacuum tank with an absolute pressure of from 0.9 to 0.1 bar, which tank is partially filled with feed in the form of emulsions and/or mud being treated, and is such that there is a vapour pocket at the top of the vacuum tank; a feed line for leading heated feed from the heater into the vacuum tank; a vapour outlet for extracting vapour from the vacuum tank; a liquid outlet for extracting liquid from the vacuum tank; and a particle outlet for extracting solids and liquid from the bottom of the vacuum tank

The heater preferably comprises a pipe that is preferably at least 25 m, more preferably at least 50 m, and most preferably at least 100 m long, and where the pipe is heated externally, preferably by surrounding hot water.

According to a first preferred embodiment, the feed line leads to a nozzle at or near the top of the vacuum tank.

According to a second preferred embodiment, the feed line discharges in a horizontally delimited region immediately below the liquid surface in the vacuum tank.

Without wishing to be bound by any specific theory for the operation of the present device, it has been assumed that at least five effects are important for the present device to produce the desired effect.

Firstly, it is important for all the components of an emulsion to be heated to approximately the same temperature. By traditional heating of a water-in-oil emulsion, most of the heat will normally be taken up by the oil, as this is the continuous phase.

There is very little in the way of heat transfer between oil and water in a solids- stabilise emulsion, as the oil acts as a thermal insulator. In e. g. a water-in-oil emulsion, the oil may thus be above the boiling temperature of water for a long time without the water getting hot enough to boil.

By heating in a heater with a large surface area, where the emulsion passes/is fed through a long pipe, all the components of the emulsion will be brought into contact with the surface of the pipe and be heated. This appears to be an important element of the present invention.

Secondly, electrical charges and static potential contributes towards stabilising the emulsion by dispersed particles in the continuous phase with the same charge repelling each other. It is further assumed that movable particles in an emulsion can be discharged by contact with the pipe wall, and that the repulsion effect is neutralised.

This is supported by evidence that points to particles becoming electrically charged following a collision with the pipe wall, which again leads to particles that are already electrically charged becoming discharged, and an emulsion may thereby be destabilised.

See for example K. Min and B. T. Chao. Nuclear Science and Engineering. 26,534- 546 (1966) As a third point, conditioning of the feed (mud and/or emulsion) through regulation of the pH is of great importance, as such a technique weakens the adsorbed film that surrounds the water droplets and acts as a physical barrier preventing contact between the dispersed water droplets. The chemical composition of this film is mentioned above.

The strength of this film is essential to the stability of an emulsion. A person skilled in the art of separating emulsions will normally be aware of which pH lies within the optimum window for a certain type of emulsion.

As a fourth point, the negative pressure in the vacuum tank is important. At a negative pressure, the components of the emulsion will boil at a lower temperature than they would at atmospheric pressure. Boiling (vapour generation) inside the droplets of the emulsion cause the droplets to burst due to the increase in vapour volume, and the emulsion is weakened/broken.

Breaking the emulsion may cause the re-formation of static charges. These new charges will inhibit further separation by the oil and water phases not becoming clean, and thus necessitating further treatment by use of a different technology. By initiating the weakening/breaking of the emulsion in the heater, new static charges will be removed in the heater. The charges are rapidly discharged through contact with steel pipe in the heater and steel walls in the vacuum tank.

As a fifth point, the negative pressure also appears to have a positive effect on the solids in the emulsion. The solid particles may contain gas pockets or in other ways associated gas. This gas can reduce the apparent density of the particles, thus preventing/reducing precipitation. By exposing the particles to heat followed by a vacuum, the gas will be

released. The resulting increase in density combined with the effect of a reduction in the viscosity and density of the oil, which according to Stoke's Law entails less resistance to the particles settling (precipitating), may be an explanation of why extremely small and fine particles of colloidal size (< 2 urn) settle following treatment according to the present method.

Certain types of mud such as used drilling mud provide special challenges, as they may in addition to microparticles such as clay and drilling fines also contain various other solids in the form of wool, sawdust, animal hair and other sealing compounds that are used to prevent drilling mud from leaking into the formation during drilling. Due to these solids, pipes smaller than 20 mm are easily blocked by used drilling mud. For this reason, certain reservations are normally made regarding the dimensions of pipes and orifices for a treatment plant for oily wastes containing large amounts of fibrous materials. Nozzles with a large pressure drop can not be used in this connection.

In the following, the invention will be described in greater detail with reference to a plant for implementing the method, in which: Figure 1 shows a schematic diagram of a plant according to the invention; Figure 2 shows a section through a vacuum tank in a plant according to the invention; Figure 3 shows a section through an alternative vacuum tank.

The plant shown in Figure 1 is a typical plant for treating various types of emulsions, such as used drilling mud or refinery sludge.

After conditioning, the emulsion to be separated is fed into the plant through an inlet 1 to a pump 2. From pump 2, the emulsion is pumped through a pipe 3 to a heater 4. The heater is a heater with a large heat transfer area, a heater comprising a long, preferably helical pipe with a smooth inner surface where the pipe is heated from the outside, preferably by means of water surrounding the coil. The heater 4 may if desired contain two or more coils connected in parallel.

The heating temperature may vary, all according to the composition of the emulsion to be separated. The temperature of the emulsion exiting the heater 4 will typically be in the range from 60 to 120 °C. The pressure in the heater 4 is preferably below atmospheric pressure, so as to subject the feed to vapour distillation already at this point. As a result, the feed in the form of emulsions is already more or less broken up before it enters the vacuum tank 10.

From the heater 4, the heated emulsion is passed through a pipe 6 via a three-way valve 7, to an upper feed line 8 or a lower feed line 9 to a vacuum tank 10. The vacuum tank 10 is partially filled with emulsion being treated. Above the surface of the emulsion is a vapour pocket 13, indicated by broken lines in the figure.

The pressure in the vacuum tank is preferably from about 0.9 bar to 0.1 bar absolute pressure. It has proven practical in several tests to work at an absolute pressure in the region 0.8-0.5 bar. Lower pressures are evaluated as required.

When treating emulsions that contain a relatively small amount of solid particles and that are otherwise highly stable, the three-way valve 7 is set so as to lead the emulsion through the upper feed line 8 to the top of the vacuum tank 10, via a nozzle 11. The nozzle is an omnidirectional spray nozzle that sprays the incoming emulsion against a hemispherical device in the upper part of the vacuum tank, causing the emulsion to run down along the walls of the tank and into the liquid phase being treated below.

The hot liquid streaming down the walls of the vacuum tank 10 will boil due to the negative pressure in the tank, and vapour and gas is released in vapour pocket 13.

When treating less stable emulsions containing a rather larger amount of solids and/or fibrous materials or other materials that may block pipes and nozzles, the three-way valve 7 is set so as to lead the emulsion through the lower feed line 9. The lower feed line enters the vacuum tank and preferably discharges immediately below the surface of the liquid in the tank, inside an essentially vertical stabilising tube 12.

Inside the stabilising tube 12, the feed line 9 is approximately horizontal. The end of the feed pipe 9 is preferably cut at an angle, such that the opening faces upward in an oblique manner, as indicated in Figure 2.

The residual emulsion flowing into the vacuum tank 10 through the feed line 9 will boil as a result of the negative pressure. Some of the liquid phase will vapourise/gasify and carry with it some of the emulsion that splashes over the edge of the stabilising tube 12.

The stabilising tube 12 has a diameter that is greater than that of the feed line, typically three to ten times larger. The diameter of the stabilising tube 12 is in turn from about 1/4 to o of the diameter of the vacuum tank 10.

Gas and vapour that is released during boiling, whether the emulsion is introduced through the upper or the lower feed line 8,9, is extracted through a gas outlet 14 by a pump 20.

The boiling of the emulsion, whether the emulsion is introduced through the upper or the lower feed line 8,9, causes the temperature of the emulsion to fall below the boiling point of the mixture, so that only the freshly added liquid boils. The boiling in the vacuum tank is thus limited to the liquid that flows down the tank walls around the vapour pocket 13 or inside the stabilising tube.

The lower part of the vacuum tank 10, i. e. that part which is filled with liquid, acts as a settling tank in which the particles that have now detached from the emulsion fall towards the bottom and can be removed through a particle outlet 16 by a pump 17. A mixture of water and oil and a limited amount of particles are removed through a liquid outlet 15 by a pump 21.

The gas in the gas outlet 14 is cooled and liquefied in a cooler 18. The cooler 18 is a cooler with a large inner surface, preferably a cooler in which the gas to be cooled is led through a helical pipe surrounded by water. The construction of the cooler 18 is thus the same as that of the heater 4.

The liquid phase from the vacuum tank 10 is extracted through the liquid outlet 15 and through a cooler 19 that is preferably of the same type as cooler 18.

The pressure in the vacuum tank is adjusted by balancing the supply of liquid through the feed line 8,9 with the extraction of liquid, mud and vapour through outlets 16,15 and 14 respectively.

After being cooled to typically about 40-60 °C, both the liquefied gas and the liquid is fed to an oil/water separator 22. This oil/water separator 22 is preferably a separator of the same type as that described in Norwegian patent application no. 19984054, or possibly a modification of this.

In oil/water separator 22, water and oil are separated into two relatively pure phases that are removed through an oil outlet 23 and a water outlet 24 respectively. Remaining particles and material heavier than water is removed through a mud outlet 25 and led to pipe 3, from where it again passes through the plant.

If required, an additional settling tank may be provided between the cooler 18 and the oil/water separator 22 in order to separate oil and water. If such an additional tank is put in, it will be possible to recover oil that is pure enough to be used without going through the oil/water separator 22. However the water normally contains impurities and should normally be cleaned further in oil/water separator 22.

The water in water outlet 24 from oil/water separator 22 may contain particles, for example organic grease particles that are particularly difficult to separate out. In such cases it may be necessary to remove such particles from the water by other traditional techniques such as filtration etc.

The embodiment shown in Figures 1 and 2 may as previously mentioned be used both for emulsions containing fibres and other materials that blocks up nozzles, in addition to emulsions without such contents. If the device is to be installed in a plant that handles the same type of emulsion on a more continuous basis, such a plant may be tailored and simplified.

Figure 3 shows an alternative embodiment with a stabilising tube 25 that is open to the rest of the vacuum tank at the top, but not at the bottom. This device is especially adapted to feeds with a very high solids content.

Mud with a high dry solids content is removed by use of a pump 27, through a mud outlet 26 at the bottom of the stabilising tube 25. Gas and vapour from the gas outlet 14 and the liquid outlet 15 are treated in the same manner as in the device described above.

Mud and water that sinks to the bottom of the vacuum tank 10 passes on to further treatment together with the mud from mud outlet 26 if the solids content is sufficiently high, or is otherwise recycled through the plant.

In order to ensure energy optimisation of the present method, the heat from the coolers 16,18 is preferably used to pre-heat the feed in the form of emulsion/mud before this is fed to the heater 4.

It is important for all the pumps to be"gentle"when handling the emulsion/mud feed.

Here, use may be made of gear pumps, eccentric screw pumps or preferably rotary lobe pumps.

Test results/comparison (s) Feed material: Slopmud Volume: Approx. l in ; Oil content: 22 vol. %; Water content: 72 vol. %; Solids: 6 vol. % (based on retort analyses) Initial density : 1. 02 kg/l, measured mud weight.

Plant operating conditions: Operating temperature, i. e. heating temperature out of heater : 87 ° C Operating pressure in vacuum tank:-0.4 bar (i. e. 0.4 bar below atmospheric pressure).

Operating mode: Feed introduced through the lower feed line.

Flow rate: Approx. I m 3/hour

Test results: Quantity of cleaned oil from outlet 23: 120 litres Density of oil from outlet 23: 0.82 (Measured by density meter from Anton Parr Dema 35 n) Quantity of cleaned water from outlet 24: Approx. 650 litres of water with particles, density 1.04 Quantity of mud returned in outlet 16: Approx. 80 litres Consistency: 60 vol. % solids Mud density: 2.62 kg/1 The remainder of the oil is in the solids, which mainly consists of light bentonite particles that have been chemically modified to swell in oil instead of water.

A lighter phase was also observed above the heavy phase, containing 40-50 vol. % solids. This share amounted to just over 20 litres. The rest of the dust was distributed as small particles in the water phase.